Two-Step Random Access in 5G Unlicensed Bands
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Solution Overview
Problem
In wireless communication systems using 3GPP 5G new radio (NR) technology in unlicensed bands, two-step random access methods are needed to reduce collisions due to contention, thereby increasing the success rate and reducing delays in random access procedures.
Innovation Solution
A method involving a terminal receiving a radio resource control (RRC) message for reconfiguration with sync, including dedicated resources and modulation and coding schemes for physical uplink shared channels, to transmit a random access preamble and payload to a second base station, and receiving a response message, optimizing the random access process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional four-step random access procedure is used in unlicensed bands, then the procedure is well-established and compatible with existing systems, but collision due to contention increases and success rate decreases
Solution Approach 1:
The patent segments the traditional four-step random access procedure into a more efficient two-step procedure by combining message 1 and message 3 into MsgA, and combining message 2 and message 4 into MsgB. This segmentation reduces the number of interaction steps and minimizes contention opportunities, thereby reducing collisions and improving success rate in unlicensed band random access.
Solution Approach 2:
The patent applies preliminary action by pre-configuring dedicated random access resources (time, frequency, and code domains) for MsgA transmission before the actual random access occurs. The base station pre-allocates specific PRACH resources and PUSCH resources, and pre-sends RRC reconfiguration messages with sync information, allowing the terminal to perform random access without contention on previously contested resources.
2Reliability
If two-step random access procedure is implemented to reduce collisions, then success rate increases, but procedure complexity increases
Solution Approach 1:
The patent merges multiple messages into fewer transmissions: MsgA combines the random access preamble (original Msg1) and uplink data (original Msg3), while MsgB combines the random access response (original Msg2) and contention resolution (original Msg4). This merging reduces the number of separate procedure steps from four to two, simplifying the overall procedure while maintaining reliability.
3Reliability
If dedicated resources are allocated for two-step random access, then collision is reduced and success rate increases, but resource management complexity increases
Solution Approach 1:
The patent applies local quality by allocating specific dedicated resources (time-frequency-code combinations) for two-step random access in certain unlicensed band scenarios, while maintaining traditional four-step procedure in other scenarios. The system selectively applies different random access procedures based on local conditions such as traffic type (eMBB vs. URLLC), channel conditions, and base station configuration, optimizing resource management for each specific case.
Data Source
Figure 1a~1b
Figure 1c
Figure 1d
AI summary
The disclosure relates to a communication technique for convergence of a fifth-generation (5G) or pre-5G communication system for supporting a higher data transmission rate beyond a fourth-generation (4G) communication system, such as Long-Term Evolution (LTE), with an IoT technology, and a system therefor. The disclosure may be applied to an intelligent service (for example, smart home, smart building, smart city, smart car or connected car, health care, digital education, retail business, security and safety-related service, etc.) on the basis of a 5G communication technology and an IoT-related technology. A method and an apparatus is provided for applying two-step random access when 3rd generation partnership project (3GPP) 5G new radio (NR) technology is used in an unlicensed band.